Sigma 30mm start-up buzz
To recover from bad state, an alternative to the off/on power cycling is to press the playback button. Note that it only takes one press to make the camera operational again (a 2nd press activates playback).
I guess the issue does impair my camera usage. When powering on, I'm conscious about pointing the camera down. What's worse, I fear this might be a symptom of some malfunction that might become unrecoverable out in the field, while carrying only one lens.
Hence, I consider having it replaced, especially if no one else can reproduce the issue.
Thanks everyone for the input.